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<meta name="keywords"
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<meta name="author" content="Luís Almeida">
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<title>jQuery Unveil - A very lightweight plugin to lazy load
	images</title>
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<script src="//ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
<script>window.jQuery || document.write('<script src="jquery-1.9.1.min.js"><\/script>')</script>
<script src="jquery.unveil.js"></script>

<script>
    $(function() {
        $("li img").unveil(300);
    });
    </script>

<body>

	<header>
		<h1>
			Unveil<small>.js</small>
		</h1>
		<p>A very lightweight plugin to lazy load images for jQuery or
			Zepto.js</p>

		<iframe
			src="http://ghbtns.com/github-btn.html?user=luis-almeida&repo=unveil&type=watch"
			allowtransparency="true" frameborder="0" scrolling="0" width="55"
			height="20"></iframe>
		<iframe
			src="http://ghbtns.com/github-btn.html?user=luis-almeida&repo=unveil&type=fork"
			allowtransparency="true" frameborder="0" scrolling="0" width="55"
			height="20"></iframe>
		<a href="https://twitter.com/share" class="twitter-share-button"
			data-text="unveil.js - A very lightweight plugin to lazy load images"
			data-via="lmgalmeida" data-related="lmgalmeida" data-count="none">Tweet</a>
	</header>

	<p>
		Most of us are familiar with the <a target="_blank"
			href="http://www.appelsiini.net/projects/lazyload">Lazy Load</a>
		plugin by <a target="_blank" href="http://www.appelsiini.net/">Mika
			Tuupola</a>.
	<p>This plugin is very useful and it boosts performance delaying
		loading of images in long web pages because images outside of viewport
		(visible part of web page) won't be loaded until the user scrolls to
		them.</p>
	<p>Lazy Load has some cool options such as custom effects,
		container, events or data attribute. If you're not gonna use any of
		them you can reduce the file size by leaving just the essential code
		to show the images.</p>
	<p>
		That's what I did and this is my lightweight version of Lazy Load with
		support for serving high-resolution images to devices with retina
		displays - <strong>less than 1k</strong>.
	</p>

	<h2>Usage</h2>
	<p>Use a placeholder image in the src attribute - something to be
		displayed while the original image loads - and include the actual
		image source in a "data-src" attribute.</p>
	<p>If you want to serve high-resolution images to devices with
		retina displays, you just have to include the source for those images
		in a "data-src-retina" attribute.</p>
	<p>You don't need to include a "data-src-retina" attribute in all
		the image tags, unveil is smart enough to fallback to "data-src" or
		even do nothing in case there isn't any "data-src" specified.</p>
	<code>
		&lt;img <span class="blue">src=</span><span class="red">"bg.png"</span>
		<span class="blue">data-src=</span><span class="red">"img1.jpg"</span>
		/>
	</code>
	<br>
	<code>
		&lt;img <span class="blue">src=</span><span class="red">"bg.png"</span>
		<span class="blue">data-src=</span><span class="red">"img2.jpg"</span>
		<span class="blue">data-src-retina=</span><span class="red">"img2-retina.jpg"</span>
		/>
	</code>
	<br>
	<p>If you care about users without javascript enabled, you can
		include the original image inside a &lt;noscript&gt; tag:</p>
	<code>
		&lt;noscript&gt;<br>&nbsp;&nbsp;&lt;img <span class="blue">src=</span><span
			class="red">"img1.jpg"</span> /><br>&lt;/noscript&gt;
	</code>
	<br>
	<br>
	<p>Run the script on document ready:</p>
	<code>
		$(<span class="blue">document</span>).ready(<span class="blue">function</span>()
		{<br> &nbsp;&nbsp;$(<span class="red">"img"</span>).unveil();<br>
		});
	</code>

	<h2>Threshold</h2>
	<p>By default, images are only loaded and "unveiled" when the user
		scrolls to them and they became visible on the screen.</p>
	<p>If you want your images to load earlier than that, lets say
		200px before they appear on the screen, you just have to:</p>
	<code>
		$(<span class="red">"img"</span>).unveil(<span class="purple">200</span>);
	</code>

	<h2>Callback</h2>
	<p>As a second parameter you can also specify a callback function
		that will fire after an image as been "unveiled".</p>
	<p>
		Inside the callback function
		<code>this</code>
		refers to the image's DOM node, so with the help of CSS3 (or jQuery
		animations) and by attaching a simple load event you can easily add
		some fancy entrance animation to your images:
	</p>
	<code>
		<span class="blue">img</span> {<br> &nbsp;&nbsp;opacity: 0;<br>
		&nbsp;&nbsp;transition: opacity .3s ease-in;<br> }
	</code>
	<br>
	<br>
	<code>
		$(<span class="red">"img"</span>).unveil(<span class="purple">200</span>,
		<span class="blue">function</span>() {<br>
		&nbsp;&nbsp;$(this).load(<span class="blue">function</span>() {<br>
		&nbsp;&nbsp;&nbsp;&nbsp;this.style.opacity = 1;<br>
		&nbsp;&nbsp;});<br> });
	</code>

	<h2>Trigger</h2>
	<p>You can still trigger image loading whenever you need.</p>
	<p>All you have to do is select the images you want to "unveil" and
		trigger the event:</p>
	<code>
		$(<span class="red">"img"</span>).trigger(<span class="red">"unveil"</span>);
	</code>

	<h2>Demo</h2>
	<p>
		The images were taken from the The Fox is Black <a
			href="http://www.thefoxisblack.com/category/the-desktop-wallpaper-project/">Desktop
			Wallpaper Project</a> - cool stuff!
	</p>
	<p>If you're on a "normal" display, unveil will load the low
		resolution version (800x500). In case you're on a device with a retina
		display, the high resolution version (1280x800 in this case) will be
		loaded instead.</p>
	<p>Scroll down to see it working.</p>

	<ul>
		<li><img src="img/loader.gif"
			data-src="img/anti-bullying-tom-froese-wallpaper-800x500.jpg"
			data-src-retina="img/anti-bullying-tom-froese-wallpaper-1280x800.jpg" /></li>
		<li><img src="img/loader.gif"
			data-src="img/brock-davis-wallpaper-800x500.jpg"
			data-src-retina="img/brock-davis-wallpaper-1280x800.jpg" /></li>
		<li><img src="img/loader.gif"
			data-src="img/dark-igloo-wallpaper-800x500.jpg"
			data-src-retina="img/dark-igloo-wallpaper-800x500.jpg" /></li>
		<li><img src="img/loader.gif"
			data-src="img/dark-igloo-wallpaper-1-800x500.jpg"
			data-src-retina="img/dark-igloo-wallpaper-1-800x500.jpg" /></li>
		<li><img src="img/loader.gif"
			data-src="img/iceland-smojr-wallpaper-800x500.jpg"
			data-src-retina="img/iceland-smjor-wallpaper-1280x800.jpg" /></li>
		<li><img src="img/loader.gif"
			data-src="img/james-olstein-wallpaper-800x500.jpg"
			data-src-retina="img/james-olstein-wallpaper-1280x800.jpg" /></li>
		<li><img src="img/loader.gif"
			data-src="img/johanna-basford-wallpaper-800x500.jpg"
			data-src-retina="img/johanna-basford-wallpaper-1280x800.jpg" /></li>
		<li><img src="img/loader.gif"
			data-src="img/Jude_Landry_Wallpaper_800x500.jpg"
			data-src-retina="img/Jude_Landry_Wallpaper_1280x800.jpg" /></li>
		<li><img src="img/loader.gif"
			data-src="img/julieta-felix-wallpaper-800x500.jpg"
			data-src-retina="img/julieta-felix-wallpaper-1280x800.jpg" /></li>
		<li><img src="img/loader.gif"
			data-src="img/Timothy-J-Reynolds-wallpaper-800x500.jpg"
			data-src-retina="img/Timothy-J-Reynolds-wallpaper-1280x800.jpg" /></li>
		<li><img src="img/loader.gif"
			data-src="img/haik-avanian-wallpaper-800x500.jpg"
			data-src-retina="img/haik-avanian-wallpaper-1280x800.jpg" /></li>
	</ul>

	<h2>Browser support</h2>
	<p>Compatible with All Browsers and IE7+.</p>

	<h2>Download</h2>
	<p>
		Download the script from the project page on <a
			href="https://github.com/luis-almeida/unveil">GitHub</a>.
	</p>
	<p>
		If you have any suggestion or bug to report please use github issues
		or get it touch with me on twitter - <a
			href="https://twitter.com/lmgalmeida">@lmgalmeida</a>.
	</p>

	<h2>License</h2>
	<p>
		Unveil is licensed under the <a
			href="http://opensource.org/licenses/MIT">MIT license</a>.
	</p>

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